Difficulty

The majority of Easy songs range from Lv1-6 (with exceptions of some like L, which is Lv9 for both difficulties).

The majority of Hard songs range from Lv6-9 (with exceptions of some like Alive: The New World, which is Level 1 on both difficulties).

Hard song difficulties are either higher or the same as easy song difficulties.

Here's a basic way of charting all nine difficulty levels:

Level 1: These are really dangerous songs. You might die of boredom while playing them.

Level 2: Not much harder than Level 1, really simplistic.

Level 3: Not too hard, play the game for a bit and you'll be fine.

Level 4: You might need to play a reasonable amount before you can Master these.

Level 5: Average difficulty. Not too hard, but not too easy, either.

Level 6: Play through all songs in Cytus and come back to these. You'll be able to Master them.

Level 7: These songs present a good challenge. It takes a decent amount of commitment to Master these.

Level 8: You really need to play a lot of the game in order to take these on, they'll tear any regular player apart.

Level 9: This is basically your "Expert", "Brutal", or "Nightmare" difficulty. However, some are not that hard, and some are harder. As caused by the diverse difference between some Level 8 and 9 songs, they will serve as a good indicator of your ability in Cytus.